The present invention relates to a method for processing data representing an acoustic signal to generate output data that identifies a class of a predetermined plurality of classes.
Coughing is one of the most common symptoms treated by medical practitioners and is often used to diagnose conditions such as asthma. Coughing is also a condition which is often painful and distressing for sufferers.
An assessment of a cough is typically subjective, being made by a medical practitioner during a consultation. There is no easy way to classify the severity of a cough in such a consultation. Instead, a medical practitioner must use their experience to subjectively assess the severity, and the likely cause of the cough.
One objective indication of the severity of a cough is to count the number of times a patient coughs over a period of time. Such an objective measure can be derived by monitoring a patient over a predetermined time period, and manually recording the number of coughs occurring within that time period. Although such monitoring may provide useful data, it is very labour intensive, requiring constant monitoring. Such monitoring is also intrusive to the patient.
Recently, attempts have been made to automatically and unobtrusively monitor cough events using an appropriately configured electronic device. However, such a device must distinguish cough events from environmental noises, and from speech of the subject. If such a device records a small percentage of speech as a cough, then the device will produce unreliable results, given that the time spent speaking is an order of magnitude greater than the time spent coughing.
PCT patent application publication number WO 2004/091503 discloses a method for processing signals indicative of a monitored subject's respiration, signals representative of the subject's posture and movement and signals representative of the sound made by the subject. The method uses the rib cage size (RC), the abdominal size (AB) of the subject while the subject undertakes different activities. From these measurements, the method determines an estimate of the lung volume (Vt) of the subject. By carrying out various analysis, the described method stated to be able to identify and distinguish between coughs, apnoea, hypopnoea, sighs and dyspnoea.
Although the method and apparatus described in WO 2004/091503 provides useful information, the number of sensors, and particularly the sensors worn to monitor the subject's abdomen and rib cage measurements cause such a device to be extremely uncomfortable. This is particularly undesirable given that a subject may be wearing the device for a substantial period of time.